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AC75 Hardware Interface Description
Strictly confidential / Preliminary
Table 7: Temperature dependent behavior
Sending temperature alert (2min after AC75 start-up, otherwise only if URC presentation enabled)
^SCTM_A: 1
Caution: Battery close to overtemperature limit.
^SCTM_B: 1
Caution: Bboard close to overtemperature limit.
^SCTM_A: -1
Caution: Battery close to undertemperature limit.
^SCTM_B: -1
Caution: Board close to undertemperature limit.
^SCTM_A: 0
Battery back to uncritical temperature range.
^SCTM_B: 0
Board back to uncritical temperature range.
Automatic shutdown (URC appears no matter whether or not presentation was enabled)
^SCTM_A: 2
Alert: Battery equal or beyond overtemperature limit. AC75 switches off.
^SCTM_B: 2
Alert: Board equal or beyond overtemperature limit. AC75 switches off.
^SCTM_A: -2
Alert: Battery equal or below undertemperature limit. AC75 switches off.
^SCTM_B: -2
Alert: Board equal or below undertemperature limit. AC75 switches off.
3.3.4.2
Deferred Shutdown at Extreme Temperature Conditions
In the following cases, shutdown will be deferred if a critical temperature limit is exceeded:
•
while an emergency call is in progress
•
while a call to a predefined phone number is in progress
•
during a two minute guard period after powerup. This guard period has been introduced
in order to allow the user to make an emergency call or a call to a phone number
predefined with the AT^SCTM command (see Error! Reference source not found. for
details). The start of any of these calls extends the guard period until the end of the call.
Any other network activity may be terminated by shutdown upon expiry of the guard time.
If the temperature is still out of range after the guard period expires or the call ends, the
module switches off immediately (without another alert message).
CAUTION! Automatic shutdown is a safety feature intended to prevent damage to the
module. Extended usage of the deferred shutdown functionality may result in damage to the
module, and possibly other severe consequences.
3.3.4.3
Monitoring the Board Temperature of AC75
The AT^SCTM command can also be used to check the present status of the board.
Depending on the selected mode, the read command returns the current board temperature
in degrees Celsius or only a value that indicates whether the board is within the safe or
critical temperature range. See [1] for further instructions.
3.3.4.4
Undervoltage Shutdown if Battery NTC is Present
In applications where the module's charging technique is used and an NTC is connected to
the BATT_TEMP terminal, the software constantly monitors the applied voltage. If the
measured battery voltage is no more sufficient to set up a call the following URC will be
presented:
^SBC: Undervoltage.
AC75_HD_V00.202
Page 38 of 120
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27.04.2006
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